This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We would like to investigate the yield stress behavior of blood. Particular interest is modulation of flow dynamics and arterial disease progressions due to yield stress levels. Blood is a yield stress fluid. It is a solid like gel when it is at rest and when it is sheared it starts to flow and behave like a Casson fluid. Blood rheology analysis allows us to describe several biological processes which are essential to understand human physiology and disease processes and also to design novel diagnostic and treatment procedures. Blood rheology will be represented as a Casson fluid with different degrees of Casson yield stress designating various physiological conditions. We use the Navier-Stokes equation to model arterial blood flow dynamics. The three-dimensional CT scan imagery of carotid arteries of a human subject to be used will be obtained from research and teaching biomedical image repository. The mathematical models to be used in the study are non-linear and transit in their nature and are not amenable to analytic solution, and a numerical method, finite volume method, is implemented. The numerical approach is computational intensive;as a result, the simulation will be conducted in supercomputing environment. Computational fluid dynamics software tools such us FLUENT and GAMBIT which are available at Pittsburgh Super Computing Center (PSC) will be used in simulation and visualization of data.